Type Ia supernovae within dense carbon-oxygen rich envelopes: a model for 'Super-Chandrasekhar' explosions?

TL;DR

This study models how dense circumstellar material around Type Ia supernovae affects their light curves and spectra, potentially explaining super-luminous events like SN 2009dc.

Contribution

It introduces detailed radiation hydrodynamic simulations of ejecta interacting with dense C/O-rich envelopes, offering a new explanation for super-Chandrasekhar supernovae.

Findings

Interaction causes broadening of light curves and longer rise times.

Radiation energy is emitted mainly in UV and X-ray regimes.

Models can reproduce properties of SN 2009dc.

Abstract

We investigate the consequences of fairly normal Type Ia supernovae being embedded in compact and dense envelopes of carbon and oxygen rich circumstellar material by means of detailed radiation hydrodynamic simulations. Our main focus rests on exploring the effects of the interaction between ejecta and circumstellar material on the ejecta evolution and the broad-band light curve. In our calculations, we find that a strong reverse shock efficiently decelerates and compresses the ejecta material. This leads to a significant broadening of the optical light curve, a longer rise to maximum and a slower decline in the tail phase. During the interaction, substantial radiative energy is generated, which mostly emerges in the extreme ultraviolet and X-ray regime. Only if reprocessing due to radiation-matter interactions is very efficient, a significant boost in the optical light curve is observed. We discuss these findings in particular in the context of the super-luminous event SN 2009dc. As our calculations are able to reproduce a number of its peculiar properties, we conclude that the flavour of the interaction scenario investigated in this work constitutes a promising candidate to explain such 'Super-Chandrasekhar' supernovae.